PROJECT SUMMARY/ABSTRACT The World Health Organization estimates that 80% of blindness worldwide is avoidable, yet cases are not detected early enough to prevent vision loss. To address this global burden, eye care systems must determine optimal methods for identifying people with or at risk for visual impairment. Worldwide, systems utilize a variety of community-based approaches to identify such cases, including screening for early disease with telemedicine and case detection of prevalent disease with cataract camps or community health workers. Each of these models requires varying levels of resources and ophthalmic skill, but no studies have been conducted on the comparative effectiveness or cost effectiveness of these different approaches. The overall objective of this project is to determine the effectiveness of community-based approaches to prevent blindness through a cluster-randomized trial. Communities in Nepal will be randomized to one of five arms (1) a state-of-the-art mobile screening unit employing telemedicine for screening and case detection, (2) a mobile case detection unit focused on cataract and refractive error only, (3) a cataract camp employing ophthalmic personnel, (4) a volunteer community health worker (CHW) program, and (5) no intervention. Intervention arms (arms 1-4) will target all adults aged ?50 years residing in intervention communities for screening and/or case detection. Those meeting referral criteria will be referred to Bharatpur Eye Hospital for a confirmatory diagnosis and follow-up care as needed, and will be closely monitored by study staff. Four years after implementation, a population-based census will be conducted in all study communities, and eligible adults will undergo a visual acuity assessment. To examine effectiveness and cost-effectiveness of these approaches, we will pursue three specific aims: 1) to determine whether screening is effective for reducing visual impairment relative to case detection (arm 1 vs 2); 2) to determine whether a CHW program increases the rate of cataract surgery compared to cataract camp (arm 3 vs 4); and 3) to compare the costs per line of visual impairment prevented between competing outreach programs (arms 1-5). The approach is innovative in its use of recently developed portable diagnostic technology that enables mobile, telemedicine-based screening on this large scale. In addition, the post-test only population-based assessment of visual acuity in a large trial design allows for the study of a rare event like blindness and eliminates the problem of loss to follow- up that affected previous screening trials. This research is significant because it will provide the strongest type of evidence to guide national eye health programs ? results from a randomized controlled trial. Ultimately, this trial will benefit blindness prevention programs worldwide in deciding how to allocate limited resources to screening or case detection.